Grommets that pass through a hole in a panel and are secured to the panel by cooperating forward and rearward flanges of the grommet that engage opposite sides of the panel are well known. The panel hole, of necessity has a smaller diameter than the mounting flanges that secure the grommet to the panel. See for instance, U.S. Pat. No. 5,732,440 granted to John O. Wright Mar. 31, 1998.
An ongoing challenge with such grommets is to reduce the insertion force required to push the grommet part way through the panel hole so that the forward mounting flange passes through the panel hole to engage the back side of the panel while insuring adequate retention by the forward mounting flange after it is pushed through the panel hole. Thus there is a need for a grommet that requires a relatively low insertion force to push the grommet part way through a panel hole while providing a relatively high retention force preventing the grommet from being pulled back out through the panel hole.
Another challenge with grommets such as those disclosed in the '440 patent is sealing around the member that passes through the grommet when the member is not round, such as in the case of a bundle of wires that pass through the grommet. While the Wright '440 does not address this problem, it is generally known to seal around non round members such as a bundle of wires with potting techniques. See for instance, U.S. Pat. No. 4,289,924 granted to Warren Peace, Jr. et al. Sep. 15, 1981.
Japanese Publications 2002-171644, 2002-171645, 2002-171646 and 2002-171647 of Jun. 14, 2002 disclose a grommet that purportedly reduces the insertion force required for mounting a grommet in a panel hole by designing the grommet so that the grommet has a collapsible bell-shaped wall leading up to a forward mounting flange. This collapsible bell shaped wall is characterized by a plurality of thick radial outer ribs joined by thin sections that have outer recesses. The collapsible bell-shaped wall also has internal radial ribs between the thin sections. In addition, the grommet has a radial wall and sleeve at the back of the rearward mounting flange that is split into two parts to facilitate collapse of the bell shaped wall upon insertion of the grommet part way into the panel hole.
The grommet disclosed in the Japanese publications is difficult to mold because of the complicated shape of the collapsible bell-shaped wall. Moreover, the grommet disclosed in the Japanese publications does not lend itself to sealing a bundle of wires or other non round member with a potting technique because of the large interior space inside the bell shaped wall and the spit radial wall and sleeve at the back of the rearward mounting flange.